Dose-dependent elimination kinetics for mercury in urine: observations in subjects with brief but high-level exposure

Abstract

Objectives: To study the elimination kinetics for mercury in urine (U-Hg) after brief but high-level exposure.

Methods: U-Hg was examined in 11 workers after 2-10 days of exposure to inorganic Hg and after symptoms and signs of Hg intoxication had appeared. Initial U-Hg excretion varied between 60 and 2360 micrograms/g creatinine. The subjects were followed up for 1-11 months. In each subject, one- and two-compartment models were fitted to the U-Hg values, assuming an exponential decrease, by weighted non-linear least-squares regression (weight = 1/U-Hg).

Results: The data indicated two elimination phases in subjects with initial U-Hg above 600 micrograms/g. In the two-compartment models, there was a fast phase with a half-time of 2-16 days, and a slow phase with a half-time of more than a month. The fast phase contributed 70-90% to the sum of the Y intercepts.

Conclusions: The kinetics of U-Hg excretion after cessation of exposure seems to be dose-dependent and, at least in certain cases, to have two phases. The explanation for the fast phase may be that the capacity of certain binding sites in the kidney was exceeded.